Brominated polstyrenic resins

ABSTRACT

Novel brominated styrenic polymers have an ionic bromine content of 2000 ppm or less, and one or more of the following additional characteristics: (a) a TGA temperature for 1% weight loss which is 340° C. or higher, and a chlorine content, if any, of less than about 700 ppm Cl (b) an actual M w  which is within about 20% of the calculated theoretical M w , the theoretical M w  being based upon the actual bromine content of the brominated styrenic polymer and the M w  of the styrenic polymer reactant used to produce the brominated styrenic polymer; and (c) essentially no content of impurities selected from the group consisting of ethylene dichloride, bromodichloroethane, dibromochloroethane, dibromodichloroethane, and tribromochloroethane. Such flame retardant polymers exhibit superior performance qualities during use, especially in thermoplastics such as glass-filled polyesters and glass-filled nylons.

RELATED APPLICATIONS

This application is a continuation-in-part of commonly-ownedapplications Ser. No. 08/852,462, filed May 7, 1997 and Ser. No.08/872,985, filed Jun. 11, 1997, now U.S. Pat. No. 5,852,132. Ser. No.08/852,462 in turn is a continuation-in-part of commonly-ownedapplication Ser. No. 08/727,341, filed Sep. 26, 1996, now U.S. Pat. No.5,677,390, issued Oct. 14, 1997. Ser. No. 08/872,985 in turn is acontinuation of commonly-owned application Ser. No. 08/727,341 filedSep. 26, 1996, now U.S. Pat. No. 5,677,390, issued Oct. 14, 1997.

BACKGROUND OF THE INVENTION

This invention relates to novel, improved high quality brominatedstyrenic polymers eminently well suited for use as flame retardants inthermoplastic polymer compositions.

Brominated polystyrenes are well established as flame retardants for usein thermoplastics, e.g., polybutylene terephthalate, polyethyleneterephthalate and nylon (a.k.a. polyamides). Recently, interest has beenshown for expanding their use to syndiotactic polystyrene andpolycyclohexylene dimethylene terephthalate. Generally, brominatedpolystyrenes are produced by a reaction between polystyrene and abrominating agent (e.g., bromine or bromine chloride) in the presence ofa solvent (e.g., dichloroethane) and a Lewis acid catalyst. Heretoforethe art has proffered many processes which are claimed to produce asuperior brominated polystyrene. See U.S. Pat. Nos. 4,200,703;4,352,909; 4,975,496 and 5,532,322.

Despite these efforts, previously-known brominated polystyrene flameretardants remain deficient in certain properties which translate intodeficient performance of thermoplastic polymer blends in which they areused when the blends are subjected to polymer processing conditions.

For example, prior art brominated polystyrene polymers that have beenevaluated for thermal stability have exhibited a 1% weight loss attemperatures less than 336° C. when submitted to ThermogravimetricAnalysis (TGA) and, indeed, most have exhibited a 1% weight loss attemperatures around 300° C. Such low thermal stabilities areundesirable, especially under the high temperatures to which flameretarded thermoplastics formulated with such brominated polystyrenepolymers are exposed during processing.

Corrosion of metal processing equipment such as melt blenders,extruders, and molding machines, attributable to the release of hydrogenhalide under thermal processing conditions is another deficiency offlame retarded thermoplastic polymer blends made using prior brominatedpolystyrene flame retardants. In the presence of moisture, hydrogenchloride and hydrogen bromide released from the brominated polystyrenein the blend during exposure to the elevated polymer processingtemperatures can result in acid formation and consequent metalcorrosion.

The bromine content of a brominated polystyrene is the sum of (1) thebromine which is substituted onto the aromatic portions of the polymer,(2) the bromine which is substituted onto the aliphatic portion(s) ofthe polymer, e.g., the polymer backbone or alkyl substitution which ispresent due to alkylation of the aromatic portion of the polymer, and(3) any ionic bromine present, e.g., sodium bromide. The alkylation ofaromatic rings in the brominated polystyrene is catalyzed by the Lewisacid catalyst used in producing the brominated styrenic polymer, and thereaction solvent (usually a 1-3 carbon atom dihaloalkane) serves as thealkylating agent. The bromine for (1) is referred to herein as aromaticbromide, while the bromine for (2) is referred to as aliphatic bromide.Even though ionic bromine can contribute to the total bromine content,its contribution to the total bromine content is small. Nevertheless, aspointed out in U.S. Pat. No. 5,328,983, ionic impurities in brominatedpolystyrene may degrade polymer formulations in respect to theirultimate electrical properties, and also may result in corrosion ofprocessing equipment or in the corrosion of metallic parts in theirend-use applications.

The chlorine content of brominated polystyrenes is credited to chlorinewhich, like the bromine, is chiefly part of the polymer structure as anaromatic and/or an alkyl chloride. The use of bromine chloride as thebrominating agent is the largest contributor to the chlorine content.However, chlorinated solvents and/or chlorine-containing catalysts usedin the production of the brominated polystyrene may also contribute tothe chlorine content of the brominated polystyrene.

The aliphatic halide content of the brominated polystyrene is notdesirable as aliphatic halide is not as thermally stable as aromatichalide and, thus, aliphatic halide can be easily converted to hydrogenhalide, e.g., HBr or HCl, under normal end-use processing conditions.Aliphatic bromide and chloride are generally referred to by the art andquantified, respectively, as hydrolyzable bromide and hydrolyzablechloride since such halides are easily hydrolyzed as compared toaromatic halides.

To evaluate brominated styrenic polymers for their tendencies to releasehydrogen halide under thermal processing conditions, use is made of themethod described in U.S. Pat. No. 5,726,252 and referred to therein asthe Thermal Stability Test Procedure. In essence, this method indicatesthe content of halogen atoms in the brominated polystyrene that is notbonded directly to the aromatic rings and, thus, is more readilyreleased from the polymer when at elevated temperature. The ThermalStability Test is described in greater detail hereinafter.

Apart from whether the halide is present as an aromatic or aliphatichalide, it is also desirable to minimize the total chlorine content ofthe brominated polystyrene as chlorine is not as efficacious or asstable a flame retardant constituent as is bromine.

Additionally, it has been demonstrated that prior art processes for themanufacture of brominated polystyrene give rise to significant cleavageof the polymer chain. This cleavage results in the produced brominatedpolystyrene having an M_(w), as measured by Gel PermeationChromatography, which is significantly lower than the calculatedtheoretical M_(w) of the brominated polystyrene. The calculation isbased upon the bromine content (wt %) of the brominated polystyreneproduct and the M_(w) of the polystyrene reactant at reactioninitiation. It is advantageous if the theoretical M_(w) and the actualM_(w) of the produced brominated polystyrene are close to each other,given the ± margins of error for GPC, since such closeness evidences apaucity of polymer cleavage. The degree of cleavage should be minimizedsince cleavage results in an increase of alkyl end groups in thebrominated polystyrene, which alkyl end groups provide loci for thefacile formation of the undesirable hydrolyzable halides discussedabove. Conversely, if cross-linking occurs, the molecular weight of thebrominated polystyrene is increased, and if not controlled, suchcross-linking can result in formation of insoluble residues and/orgelation of the reaction mixture. In addition, viscosity specificationsrelated to end product usage can be disrupted by such undesirableincreases in molecular weight.

It would be especially desirable if most if not all of theabove-mentioned disadvantages of brominated polystyrenes could beavoided or at least minimized. For example, it would be of considerableadvantage, especially for achieving better electrical properties inconnection with nylon flame retardant usage, if a more thermally stablebrominated styrenic polymer, e.g., brominated polystyrene, could beprovided that also has a suitably low ionic bromine content. Anotherexample of a welcome contribution to the art would be the provision of abrominated polystyrene styrene polymer in which the theoretical M_(w)and the actual M_(w) of the produced brominated polystyrene are close toeach other and in which the content of ionic bromine is sufficiently lowfor inclusion in polymers used in electrical applications, such asglass-filled nylon polymers.

This invention is deemed to at least minimize, if not overcome, most, ifnot all, of the above-mentioned disadvantages of brominatedpolystyrenes.

SUMMARY OF THE INVENTION

In accordance with this invention, new, high quality brominated styrenicpolymers having suitably low ionic bromine contents are provided. Inaddition, these new brominated styrenic polymers possess or exhibitother superior properties or characteristics enhancing their utility asflame retardants for thermoplastic polymers of various types, includingglass-filled polyesters and glass-filled nylons.

Thus, pursuant to one embodiment of this invention there is provided abrominated styrenic polymer, preferably a brominated polystyrene, thathas (i) a TGA temperature for 1% weight loss which is 340° C. or higher,preferably within the range of from about 340° C. to about 380° C., andmore preferably within the range of from about 345° C. to about 380° C.,and a chlorine content, if any, of less than about 700 ppm Cl,preferably less than 500 ppm Cl, and more preferably less than 100 ppmCl, and (ii) an ionic bromine content of 2000 ppm or less, preferably1500 ppm or less, more preferably 1000 ppm or less, and most preferably500 ppm or less, all such ppm levels being based on the total weight ofthe brominated styrenic polymer.

In another embodiment of this invention there is provided a brominatedstyrenic polymer, preferably brominated polystyrene, that has an actualM_(w) which is within about 20%, and preferably within about 10%, of itscalculated theoretical M_(w), the theoretical M_(w) being based upon theactual bromine content of the brominated styrenic polymer and the M_(w)of the styrenic polymer reactant used to produce the brominated styrenicpolymer, and that has an ionic bromine content of 2000 ppm or less,preferably 1500 ppm or less, more preferably 1000 ppm or less, and mostpreferably 500 ppm or less. Preferably, such brominated styrenic polymeris also characterized (i) by containing less than about 700 ppm Cl,preferably less than 500 ppm Cl, and more preferably less than 100 ppmCl and/or (ii) by having a TGA temperature for 1% weight loss which is340° C. or higher, preferably within the range of from about 340° C. toabout 380° C., and more preferably within the range of from about 345°C. to about 380° C.

A further embodiment of this invention is a brominated styrenic polymer,preferably brominated polystyrene, that is essentially free ofimpurities selected from the group consisting of (a) methylene chloride,(b) ethylene dichloride, and especially (c) bromodichloroethane, (d)dibromochloroethane, (e) dibromodichloroethane, (f)tribromochloroethane, and (g) any mixture of two or more of theforegoing, especially a mixture that contains at least one of (c)through (f), and that has an ionic bromine content of 2000 ppm or less,preferably 1500 ppm or less, more preferably 1000 ppm or less, and mostpreferably 500 ppm or less. In additional alternative preferredembodiments such brominated styrenic polymer is also characterized (i)by containing, if any, less than about 700 ppm Cl, preferably less than500 ppm Cl, and more preferably less than 100 ppm Cl and/or (ii) byhaving a TGA temperature for 1% weight loss which is 340° C. or higher,preferably within the range of from about 340° C. to about 380° C., andmore preferably within the range of from about 345° C. to about 380° C.,and/or (iii) by having a thermal stability in the Thermal Stability Testdescribed hereinafter of 1500 ppm HBr or less, preferably 1000 ppm ofHBr or less, and more preferably 500 ppm of HBr or less, and/or (iv) byhaving an actual M_(w) which is within about 20%, and preferably withinabout 10%, of its calculated theoretical M_(w), the theoretical M_(w)being based upon the actual bromine content of the brominated styrenicpolymer and the M_(w) of the styrenic polymer reactant used to producethe brominated styrenic polymer.

In each of the above embodiments the brominated styrenic polymer,preferably a brominated polystyrene, additionally has a thermalstability in the Thermal Stability Test described hereinafter of 1500ppm HBr or less, preferably 1000 ppm of HBr or less, more preferably 500ppm of HBr or less, and most preferably 200 ppm of HBr or less (e.g., aslittle as 100 ppm of HBr or less), all such ppm levels being based onthe total weight of the brominated styrenic polymer.

Each of the brominated polymer compositions of this invention describedabove preferably has a total bromine content of at least 50 wt %, morepreferably at least 60 wt %, and most preferably at least about 67 wt %(e.g., in the range of about 68-71 wt %).

Other embodiments and features of this invention will be furtherapparent from the ensuing description and appended claims.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram depicting a process suitable for producingpreferred brominated polystyrenes of this invention.

FURTHER DETAILED DESCRIPTION Brominated Styrenic Polymers

As noted above, the brominated styrenic polymers of this invention arebrominated styrenic polymers, (preferably a brominated polystyrene).These brominated styrenic polymers have a total bromine content of atleast about 50 wt %, preferably above about 60 wt %, and more preferablyat least about 67 wt %; and an ionic bromine content of 2000 ppm orless, preferably 1500 ppm or less, more preferably 1000 ppm or less, andmost preferably 500 ppm or less, all wt % and ppm levels herein beingbased on the total weight of the brominated styrenic polymer, unlessotherwise stated. Moreover, the brominated styrenic polymers (preferablybrominated polystyrenes) of this invention possess certain additionalimportant properties or characteristics in accordance with the aboveSummary of the Invention. These properties or characteristics pertain tosuch factors as TGA temperature for 1% weight loss, total chlorinecontent (if any), thermal stability in the Thermal Stability Testdescribed hereinafter, actual M_(w) closely matching calculatedtheoretical M_(w), and freedom from specified impurity contents. Theproperties of other suitable brominated styrenic polymers of thisinvention will be apparent as the description proceeds.

The high TGA temperatures which are characteristic of brominatedstyrenic polymers that possess the TGA characteristics specifiedhereinabove are not believed to be due to post reaction purificationtechniques. Rather, it is believed that such enhanced thermal stabilityis due to the chemical makeup of the brominated styrenic polymer itself.

As to the brominated styrenic polymers that possess the M_(w) propertiesspecified hereinabove, a difference between the actual M_(w) and thetheoretical M_(w) outside of the normal ± margin of error for GPCanalysis, is evidence of either cross-inking (increases the M_(w)) orpolymer chain cleavage (decreases the M_(w)). The 20% differencementioned above for the brominated styrenic polymers that possess thischaracteristic includes the ± margin of error. Preferred differences arethose less than about 20%, with differences of less than about 10% beingmost preferred. Since GPC techniques can give different but similarvalues for the same polymer tested, the testing is best performed bytaking the arithmetic average of five consecutive GPC determinations ofthe polymer to be tested. Other data averaging techniques are suitable,such as using the average of 10 consecutive GPC determinations withdiscard of the high and low values, the only requirement being thataccurate and reproducible results are obtained.

This invention also provides a novel thermally stable brominatedpolystyrene which is comprised of polymer units having the formula:

wherein each X is independently —H or a halide atom, the identity ofeach X for each polymer unit being such that the brominated polystyrenecontains less than about 6000 ppm of X-type halide atoms, and whereinthe value of n for each polymer unit is such that the brominatedpolystyrene contains at least 50 wt % bromine. From an economic andperformance standpoint, it is preferred that the bromine content bewithin the range of from above 60 wt % to about 70-71 wt % (n=about 1.9to about 2.9-3.0), and especially within the range of from about 68 wt %to about 71 wt % (n=about 2.7 to about 3.0).

With regard to the halide atoms, X, preferred brominated polystyreneswill be those in which X is bromide. Such polymers may contain somechlorine atoms, but the amount will be insignificant, usually less thanabout 500 ppm, and where possible, less than about 100 ppm. If chlorineis present, its source would probably be the Lewis acid catalyst or thesolvent used in the preparation of the brominated polystyrene. Preferredbrominated polystyrene polymers are those in which the chlorine contentis less than 500 ppm in accordance with X-Ray Fluorescence analysis. Itis beneficial, from the viewpoint of economy and performance, that theX-type bromide content be less than about 4000 ppm, say within the rangeof from about 1000 ppm to about 3000 ppm. Most beneficial are thoseX-type bromide contents which are within the range of from 0 ppm toabout 1500 ppm.

The brominated polystyrenes of this invention are unique in that, fromtheir very inception, the polymer has the very low X-type halide contentdiscussed above. This is an important aspect as the polymers do not needfurther treatment to reduce the X-type halide content. Reduction of theX-type halide content, say by hydrolysis, is not desirable as it yieldsa polymer having hydroxyl, ether, and/or olefinic functionality in itsstructure which can alter polymer properties. It is preferred that thebrominated polystyrenes of this invention contain little or nohydrolysis residues, say less than about 500 ppm and preferably lessthan about 100 ppm.

The most preferred brominated polystyrene components of this inventionwill be those which provide, at the lowest cost, the highest brominecontent and the lowest X-type halide content which obtain the desiredproperties referred to above.

The brominated styrenic polymers of this invention preferably exhibitadditional superior physical properties, e.g., little or no color orodor. For flame retardants, color is an important property, with purewhite being the ultimate goal. Due to the formation of various colorbodies by all bromination processes, the industry has acceptednear-white products as being acceptable. The color of prior artbrominated polystyrene, expressed as a solution ΔE value, generally willfall within the range of 20 to 35. In distinction, the brominatedpolystyrenes used pursuant to this invention typically feature ΔE values(10 wt % in chlorobenzene) of less than 20 and preferably within therange of from about 2 to about 18. Most preferably, such ΔE value willbe within the range of from about 2 to about 15.

Another physical property of the preferred brominated styrenic polymersof this invention is that they have essentially no odor, or very littleodor, when heated to a temperature above 150° C. In comparison,Pyro-Chek® 68PB brominated polystyrene flame retardant (FerroCorporation) has a noticeable and strong odor at 150° C. The strong odoris believed to be attributable to the presence of bromochloroethanes,e.g., bromodichloroethane, dibromochloroethane, dibromodichloroethaneand tribromochloroethane, which are in the Pyro-Chek® 68PB product. Suchbromochloroethanes are not seen in detectable quantities in thebrominated styrenic polymers of this invention.

Styrenic Polymer Reactants

Styrenic polymers which are brominated to form the brominated styrenicpolymers of this invention are homopolymers and copolymers of vinylaromatic monomers. Preferred vinyl aromatic monomers have the formula:

H₂C═CR—Ar

wherein R is a hydrogen atom or an alkyl group having from 1 to 4 carbonatoms and Ar is an aromatic group (including alkyl-ring substitutedaromatic groups) of from 6 to 10 carbon atoms. Examples of such monomersare styrene, alpha-methylstyrene, ortho-methylstyrene,meta-methylstyrene, para-methylstyrene, para-ethylstyrene,isopropenyltoluene, vinylnaphthalene, isopropenylnaphthalene,vinylbiphenyl, vinylanthracene, the dimethylstyrenes, tert-butylstyrene,the several bromostyrenes (such as the monobromo-, dibromo-, andtribromo- variants). Polystyrene is the preferred reactant. When thebrominated styrenic polymer is made by bromination of a copolymer of twoor more vinyl aromatic monomers, it is preferred that styrene be one ofthe monomers and that styrene comprise at least 50 weight percent of thecopolymerizable vinyl aromatic monomers. If a bromostyrenic polymer isselected for bromination to make a brominated styrenic polymer, theinitial bromostyrenic polymer must have a lower bromine content than thebromine content to be present in the brominated styrenic polymer of thisinvention. In this connection, the terms “brominated styrenic polymer”and “brominated polystyrene” as used in the specification and in theclaims hereof refer to a brominated polymer produced by bromination of apre-existing styrenic polymer such as polystyrene or a copolymer ofstyrene and at least one other vinyl aromatic monomer, as distinguishedfrom an oligomer or polymer produced by oligomerization orpolymerization of one or more brominated styrenic monomers, theproperties of the latter oligomers or polymers being considerablydifferent from brominated polystyrene in a number of respects.

The polystyrene reactant used in the production of the brominatedpolystyrenes of this invention can be any of those which arecommercially available. Generally, the polystyrene backbone will nothave been hydrogenated and, thus, will have unsaturation. There is noneed for the brominated polymers of this invention to be produced fromanionically produced polystyrene as is taught in EPO 0 201 411; in fact,it is preferred that the polystyrene reactant not be an anionicallyproduced polystyrene as such polystyrene polymers are expensive and notreadily available. The aromatic pendant constituents of the polymer canbe alkyl substituted, but in most cases, will not be so substituted. Thepolystyrene used to produce the brominated polystyrenes of thisinvention will have a M_(w) within the range of from about 500 to about500,000 and a polydispersity within the range of from above about 1 toabout 4. For most purposes, the polystyrene reactant will have a M_(w)within the range of from about 100,000 to about 300,000 and will have apolydispersity within the range of from about 1.25 to about 2.5. Thelower molecular weight polystyrene reactants will have a M_(w) withinthe range of from about 500 to about 100,000 and a polydispersity lessthan about 10 and preferably within the range of from above 1 to about4. Higher molecular weight polymer reactants of this invention have aM_(w) within the range of from about 300,000 to about 500,000 and apolydispersity within the range of from above I to about 4. The M_(w)and polydispersity values are both based on gel permeationchromatography (GPC) techniques which are hereinafter described.

It has also been found preferable that the polystyrene used in theformation of the brominated polystyrenes flame retardant not contain anyadditives, such as zinc stearate, paraffins, mineral oils and the like.A highly preferred polystyrene is Styron® 612 which is marketed by DowChemical Company. However, additive-containing polystyrene such asStyron 668, Styron 677, Styron 680 of Dow Chemical Company, as well asPiccolastic A5, Piccolastic A75, or Piccolastic D125 of HerculesIncorporated, and EA 3300, MB 3200, MC 3100, or EA 3000 of ChevronChemical Company, or equivalent materials from other producers, can beused.

Production of the Brominated Polystyrene

For purposes of simplification, much of the description hereinafterrefers to preparation of brominated polystyrene, the preferred flameretardant of this invention. It will be appreciated that the principlesand procedures described are applicable to preparation of otherbrominated styrenic polymers.

The brominated polystyrenes of this invention are not conventionallyproduced. Generally, a suitable process comprises feeding a mixture ofbromine and a solution of bromochloromethane and polystyrene (2.5 to 5moles of bromine per mole of polymerized styrene in the polystyrene) toa reactor containing a further amount of bromochloromethane and acatalytic amount of AlCl₃. The mixture of polystyrene,bromochloromethane and bromine is substantially free of a brominationcatalyst. The phrase, “substantially free of a bromination catalyst,” isto be taken to mean less than a catalytically effective amount ofcatalyst. With such low amounts of catalyst, little or no catalyzedbromination or cross-linking should occur. Generally, such amounts willbe less than 500 ppm based on the weight of polystyrene reactantpresent. The reaction temperature will be within the range of from about−10° C. to about 15° C. Preferably, the reaction is conducted at one ormore temperatures in the range of about −10° C. to about 10° C. as thisprovides product of the highest quality and, surprisingly, the reactionitself proceeds at a suitably rapid rate at these low temperatures suchthat the process meets commercial production requirements. After thereaction mass is formed, it is usually maintained at reactiontemperature for a period in the range of about 5 minutes to 2 hours, andpreferably in the range of about 5 minutes to about 60 minutes. Afterthis period, the reaction product is worked up by adding water and thensettling to remove the acidic phase. Multiple water washes can beperformed as desired. Next the reaction mass is treated with a base suchas sodium hydroxide, sodium sulfite, and/or sodium borohydride, usuallyas an aqueous solution, to adjust the reaction pH to a suitable level ofbasicity and kill any remaining brominating agent. After thesetreatments, the reaction mass is settled to obtain a two-phase reactionmass containing an organic phase, which contains, as a solute, thebrominated styrenic polymer product and an aqueous phase. The aqueousphase is decanted and the remaining organic phase is stripped of itssolvent component. It is most convenient to accomplish this strip bypumping the organic phase into boiling water. As the solvent is flashedoff, the brominated styrenic polymer product forms a precipitate. Theprecipitate can be recovered by any liquid-solid separation technique,e.g., filtration, centrifugation, etc. The recovered precipitate is thendried. If desired, a thermal stabilizing amount of base can beincorporated in the finished brominated polystyrene composition. Thatis, the finished brominated polystyrene composition can be treated tocontain an amount of alkali metal base such that if a sample of thefinished composition is dissolved in bromochloromethane and theresultant solution is extracted with water, the aqueous extract has a pHof at least about 9.0, preferably a pH in the range of about 9.5 toabout 11, and more preferably in the range of about 10 to about 10.5.Commonly-owned application Ser. No. 09/066,172, filed Apr. 24, 1998,describes processes in which a suitable amount of aqueous base isemployed to improve the thermal stability of the resultant brominatedpolystyrene. A preferred way is to suitably increase the amount of baseused during the catalyst deactivation stage so that a suitable residualamount of the base remains within the finished brominated polystyrene.

A preferred process can be used to ensure recovery of a purifiedbrominated polystyrene polymer (or other brominated styrenic polymer)having a suitably low ionic halogen content (e.g., ionic bromine orionic chlorine content) from the reaction mass formed by brominatingpolystyrene with bromine in a halocarbon or halohydrocarbon solventhaving a boiling point below 100° C. and in the presence of a Lewis acidcatalyst. Such preferred process comprises:

a) quenching the reaction mass in water to form an aqueous phase and anorganic phase, and recovering the organic phase;

b) mixing the organic phase with water at a temperature in the range ofabout 10 to about 100° C. in a ratio of from about 0.02 to about 0.6part by volume of the aqueous phase per each 1 part by volume of organicphase to form an aqueous extraction phase and an extracted organicphase, and recovering the extracted organic phase;

c) optionally but preferably, mixing inorganic alkali metal base andwater with extracted organic phase from b) to form an alkaline mixturein which the pH of the aqueous phase in this mixture is in the range ofabout 7 to 14, and preferably in the range of about 10 to 14;

d) mixing a bromine scavenger and water with alkaline mixture from c) toform a bromine scavenged mixture;

e) precipitating brominated polystyrene by mixing bromine scavengedmixture from d) with a water solution of inorganic alkali metal basemaintained at or above the boiling temperature of the halocarbon orhalohydrocarbon solvent; and

f) recovering brominated polystyrene formed as a precipitate in e).

Before proceeding to step c) above, step b) above can be repeated one ormore times as may be necessary or appropriate in achieving the desiredreduction in ionic halogen (e.g., ionic bromine). Alternatively, step b)can be conducted on a continuous basis using liquid-liquid extractionapparatus such as a liquid-liquid extraction tower. Sodium sulfite andsodium borohydride are the preferred bromine scavengers for use in stepd) above. However, other water-soluble inorganic sulfides such aslithium sulfite, potassium sulfite, magnesium sulfite, ammonium sulfite,etc., or other water soluble borohydrides such as lithium borohydride,potassium borohydride, etc., can be used. And in step d) above, acoalescing filter can be employed, if desired, to remove additionalaqueous phase from the organic phase, and thereby still further reducethe ionic halogen content of the finished product.

In the production of brominated polystyrene, it is important that theiron content be kept to a minimum, say less than about 10 ppm iron. Theintroduction of iron into the product usually occurs due to ironequipment which is in contact with the reaction and product streams.Thus, it is preferred to use process equipment which does not act as asource of iron contamination. For example, the equipment can beglass-lined or corrosion resistant alloy.

A more detailed process description with reference to the accompanyingdrawing is given below.

Detailed Description of Bromination Process with Reference to theDrawing

Preferred process technology for producing brominated polystyrenes isdescribed herein. It will be appreciated that, unless otherwiseindicated in the specification hereof or specified in any claim hereof,this invention is not limited to use of all of this preferred processtechnology.

Polystyrenes useful for the production of the brominated polystyrenes bythis preferred process are any of those which have been described above.Also, as mentioned previously, it is preferred that the polystyrene beadditive-free. Again, a most preferred polystyrene reactant is Styron612 which is marketed by Dow Chemical Company.

The catalyst used in the preferred process can be any of the aluminumbased catalysts, e.g., AlCl₃, AlBr₃ and Al. Mixtures of aluminumcatalysts can also be used. Once the catalyst has been added to thereaction system, it may undergo some reaction without significant lossof catalytic activity, e.g., AlCl₃ may convert to some extent to AlBr₃.AlCl₃, because of its availability and price, is the catalyst of choice,and powder grade AlCl₃ is most preferred due to its ease ofdispersibility.

The catalyst is used in an amount which is sufficient to obtain thecatalytic effect sought. These catalytic amounts will depend on theactivity of the catalyst, but will generally fall within the range offrom about 0.2 to about 10 weight percent and preferably within therange of from about 0.5 to about 5 weight percent, based on the weightof the styrenic polymer being brominated. The most active catalysts willbe used in the lower amounts, while the less active catalysts will beused in the higher amounts. When AlCl₃ is the catalyst, amounts withinthe range of from about 0.5 to about 3 weight percent are preferred.

The brominating agent is preferably bromine. Bromine can be obtainedcommercially in the diatomic form or can be generated by the oxidationof HBr. Br₂ can be supplied either as a liquid or a gas. The amount ofbrominating agent used in the process should provide an overall moleratio of total brominating agent to total styrenic polymer fed whichwill provide from about 1 to about 3 bromine substitutions per styrenicmonomer unit in the polymer. It is preferred that the brominatedpolystyrene contain at least about 60 wt % bromine, and desirably atleast about 68 wt % bromine and most preferably within the range of fromabout 69 to 71 wt % bromine. For any particular styrenic polymer, theamount of brominating agent used in the process will be determined bythe bromine content desired considering the highest bromine contentwhich is obtainable with the process parameters chosen. The higherbromine contents will require the most brominating agent. It is pointedout that as perbromination is approached, it becomes more difficult tosubstitute the last bromines. Adding ever larger amounts of abrominating agent does not always attenuate this difficulty. Thestoichiometry is easily determined as it requires one mole of Br₂ persubstitution sought. In practice, the practitioner will determine thebromine content sought on a weight basis and then will calculate, on anidealized basis, the number of moles of brominating agent needed toobtain the same. For example, if the styrenic polymer is polystyrene andthe bromine content sought is 68 wt %, at least 2.7 moles of bromine perstyrenic monomer unit will be required, not including any desiredstoichiometric excess.

All of the bromine can be added with the polystyrene-bromochloromethanesolution or a portion of the bromine can be pre-added to the reactorwith the remainder being added with the solution. If pre-addition is tobe used then the pre-added portion will amount to 0.5 to 20% of thetotal bromine used in the process.

While the foregoing describes the overall quantitative relationshipbetween the brominating agent and styrenic polymer, the quantitativerelationship between these two reactants in the feed mixture has notbeen fully discussed. Generally, the mixture which is to be fed isformed from about 1 to about 8 moles of brominating agent per mole ofstyrenic monomer units at any time during the feed period. During thefeed, the quantitative relationship can be constant or can vary withinthe above-mentioned range. (It is possible to allow for some excursionsoutside of the range so long as such does not do significant harm to theprocess efficiency or to product quality.) A preferred range is fromabout 2.5 to about 5 moles of brominating agent per mole of styrenicmonomer units to form the feed mixture. As can be appreciated, the useof an amount of brominating agent in the feed mixture which gives a moleratio of brominating agent to styrenic monomer units which is less thanor greater than the selected overall mole ratio of brominating agent tostyrenic monomer units will result in exhaustion of either thebrominating agent or the styrenic polymer as a mixture constituentbefore exhaustion of the other constituent. For example, if thepractitioner chooses to produce brominated polystyrene with a 70 wt %bromine content, an overall molar ratio of bromine to styrenic monomerunits of 3.0:1 would be suitable. If the practitioner chooses to form afeed mixture in which the molar ratio of bromine to styrenic monomerunits is 1:1, it can be seen that the amount of polystyrene to be fedwill be completed before obtaining the needed overall amount of bromine.In this case, the practitioner first uses the 1:1 mixture and thencontinues on with just a bromine feed after the polystyrene feed hasbeen exhausted. If, on the other hand, the molar ratio in the feedmixture is chosen to be 5:1, then the bromine will first becomeexhausted and the feed will have to be finished with the polystyrenealone. Generally, it is preferred to have the overall molar ratio andthe feed mixture ratio at least somewhat similar. In all cases though,the initial feed should preferably contain at least a molar ratio ofbromine to styrenic monomer units of 1:1.

It is preferred that the bromine used in the process be essentiallyanhydrous, ie., contain less than 100 ppm (weight basis) water andcontain no more than 10 ppm organic impurities, e.g., oil, grease,carbonyl containing hydrocarbons, iron, and the like. Available,commercial grade bromine may have such purity. If, however, such is notavailable, the organic impurities and water content of the bromine canbe conveniently reduced by mixing together a 3 to 1 volume ratio ofbromine and concentrated (94-98 percent) sulfuric acid. A two-phase mixis formed which is stirred for 10-16 hours. After stirring and settling,the sulfuric acid phase, along with the impurities and water, isseparated from the bromine phase. To further enhance the purity of thebromine, the recovered bromine phase can be subjected to distillation.

The preferred organic solvent for the bromination, namely,bromochloromethane, is preferably essentially anhydrous, containing lessthan 100 ppm (weight basis) water. It is most preferred that the solventcontain as little water as is practically obtainable, say between 0 to30 ppm (weight basis).

The process benefits from the reaction mass being in an anhydrouscondition. Water tends to affect the catalytic activity of the aluminumcatalyst, which effect may hinder the quick aromatic bromination of thestyrene rings. If, for some reason, the practitioner has large amountsof water in the process and dewatering is not practical, then it may bepossible to overcome the situation by simply increasing the amount ofcatalyst used.

By forming a solution of bromochloromethane and styrenic polymer, thepolymer becomes easy to handle and mix with bromine. These solutionspreferably contain from about 5 to about 50 wt % polymer. More highlypreferred are those which contain from about 5 to about 30 wt % polymer.

It is preferred to have the bromination catalyst, to which thebromine/styrenic polymer mixture is fed, to be in association withbromochloromethane so that the catalyst can be in a solution, slurry,dispersion or suspension. Such will enhance reaction mass mixing andmass transfer qualities. The mixture of bromochloromethane and catalystis best described as a suspension. Generally, it is suitable to use fromabout 95 to about 99.9 wt %, preferably from about 99 to about 99.8 wt%, bromochloromethane, based on the total weight of bromochloromethaneand catalyst.

The styrenic polymer/brominating agent mixture feed should occurexpeditiously, with consideration being given to the ability of theprocess equipment to handle the heat load from the exothermic process,the evolving HBr, and other process concerns. In short, the feed canoccur over the shortest time period that will be allowed by theequipment without excursion outside of critical process parameters.Generally, it is anticipated that the feed period will be from 0.5 to 3hours for a commercial-size plant. Shorter feed periods are expected forsmaller scale processes.

It is possible to conduct the bromination reaction at a temperaturewithin the range of from about −20° C. to about 60° C. Desirably, thebromination temperature is maintained within the range of from about−10° C. to about 15° C. Most preferred temperatures are in the range offrom about −10° C. to about 0° C. This last-mentioned temperature rangeprovides product of the highest quality and, surprisingly, the reactionitself proceeds at a suitably rapid rate at these low temperatures suchthat the process meets commercial production requirements. The pressurecan be atmospheric, subatmospheric or superatmospheric.

In carrying out the process, a bromination catalyst, preferably powderedAlCl₃, is suspended in essentially anhydrous bromochloromethane, to givean easily stirrable suspension. The suspension is prepared in aglass-lined, stirred reactor and brought to a temperature within therange of from about −10° C. to about −5° C. The mix is kept under aninert, dry atmosphere in the reactor. A solution of a styrenic polymerand bromochloromethane is prepared and intimately mixed with a brominestream to yield a homogenous mixture. The mixture is fed into thestirred bromination catalyst suspension in the reactor. The intimatemixing of the styrenic polymer solution and bromine can be accomplishedin a number of ways. For example, the solution and bromine can be fed toa mixing device, e.g., a mixing nozzle, at the lower end of the diptubein the reactor which extends to a point below the suspension level. Themixing device is designed to obtain the intimate mixing of the solutionand bromine. Also, the mixing device acts to impart mixing energy, atthe point of feed, to the intimate mixture and catalyst suspension.Another technique for obtaining intimate mixing of the styrenic polymersolution and brominating agent, is to use an exterior reactor loophaving an in-line mixer, such as an impingement mixer. Generally, theuse of an exterior reactor loop includes first charging the reactor witha bromination catalyst slurry, suspension, etc., and then withdrawingfrom the reactor a stream which is then fed to a mixer external of thereactor. A mixture formed from at least bromine and styrenic polymer isalso fed to the mixer to yield a second mixture which is formed from thetwo feeds to the mixer. The second mixture is subsequently fed back tothe reactor. The stream withdrawn from the reactor will initiallycomprise the catalyst. After the second mixture is fed to the reactorand the process runs, the withdrawn stream will begin to comprisebrominated polystyrene along with catalyst.

Exemplifying the use of a reactor jet mixer, reference is made to FIG. 1wherein there is shown a reactor, generally designated by the numeral10. Reactor 10 is a stirred reactor, and initially it contains asuspension comprising catalyst and bromochloromethane. Reactor dischargeconduit 40 provides a recycle stream from reactor 10 which is fed topump 50. Pump 50 pressurizes the stream so that it is fed with force viaconduit 70 back to reactor 10. Bromine is fed via conduit 20 to pump P₁while, at the same time, a solution of polystyrene andbromochloromethane is fed via conduit 22 to pump P₂. Pumps P₁ and P₂feed jet mixer 24 via lines 26 and 28, respectively, to thereby producean intimate mixture of bromine, polystyrene, and solvent. This intimatemixture is fed into the reaction mass in proximity to agitator 30 toensure thorough mixing of the reactor contents. The removal of contentsfrom, and their recycle back to, reactor 10, and also the feed of freshreactants to jet mixer 24 are continued until at least substantially allof the bromine and polystyrene/bromochloromethane solution have been fedinto the reaction mass.

As can be appreciated, the contents of reactor 10 change in compositionduring the bromine and bromochloromethane solution feeds. Initially, thecontents of reactor 10 comprise catalyst and solvent. As the processruns, the reactor contents comprise and begin to become more rich inbrominated polystyrene.

Irrespective of whether or not a diptube mixer or an exteriorimpingement mixer is used, the bromination of styrenic polymer willyield HBr as a major by-product. The HBr formed in the process firstsaturates the solvent and from then on HBr escapes into the head spaceabove the reactor contents. It is preferred that the HBr be removed andpassed to a water scrubber or stored as dry HBr. A dry, inert gas, e.g.,nitrogen, can be used as a pad over the reactor contents to minimize thepresence of water therein.

The reactor, in all cases, is preferably kept at a low temperature,e.g., from about −10° C. to about 10° C., during the feed of thestyrenic polymer and/or brominating feed, as the case may be, and mostpreferably from about −10° C. to about 5° C. Also, after the feed isaccomplished, the reactor is maintained at reaction temperature(desirably in the range of −10° C. to about 15° C. and preferably in therange of −10° C. to about 10° C.) for a period of from about 5 minutesto about 2 hours and preferably from about 5 to about 60 minutes. Suchadditional period of time following completion of the feed serves tocontinue the bromination until the desired degree of bromination hasbeen achieved. Such period will be longer if the reaction parametersprovide for mild bromination conditions during the bromine-polystyrenefeed than if the parameters chosen provide for more severe brominationconditions during the feed. Also, such period will be longer if a highdegree of bromination (e.g., above 69 wt % bromine in the brominatedpolystyrene) is sought. The reaction mass can be kept in the reactorduring the additional period of time following completion of the feed.Also, the hold period can be used to strip more HBr from the reactionmass by using an inert gas sweep.

When the desired degree of bromination has been achieved, the preferredprocess described above for recovery of a purified brominatedpolystyrene polymer having a suitably low ionic halogen contentinvolving steps a) through f) can be used. Another similar method forworking up the reaction mass is to treat the reaction mass with water todeactivate the catalyst. Then the reaction mass is settled to remove theaqueous HBr phase. Sodium sulfite or sodium borohydride, typically as anaqueous solution, can then be added (and preferably is added) to removeany remaining brominating agent, followed by sodium hydroxide, againtypically as an aqueous solution, to adjust the pH of the reaction mass.Although sodium sulfite and sodium borohydride are the preferred brominescavengers for use in removing any remaining brominating agent, otherwater-soluble inorganic sulfides such as lithium sulfite, potassiumsulfite, magnesium sulfite, ammonium sulfite, etc., or other watersoluble borohydrides such as lithium borohydride, potassium borohydride,etc., can be used in as much as the scavenging function is performed bythe sulfite or borohydride anion and/or by whatever other species mayform when the inorganic sulfite or borohydride is dissolved in water.Aqueous solutions of the sulfite or borohydride can contain any suitableconcentration of the dissolved inorganic sulfite or borohydride, and theamount of water-soluble sulfite or borohydride salt used should be atleast sufficient to react with (destroy) the amount of residualbrominating agent present in the mixture being treated. It is notnecessary or advisable to use a large excess of sulfite or borohydride,e.g., more than about 2-3 mole % excess, as the excess represents wastedmaterial serving no useful purpose. After scavenging the brominatingagent, additional sodium hydroxide or other alkali metal base can beadded, if desired, in a suitable amount and preferably in the form of anaqueous solution to act as a stabilizer for the brominated polystyrene.Whether or not such stabilizer is used, the reaction mass is settled toobtain a two-phase reaction mass containing an organic phase, whichcontains, as a solute, the brominated styrenic polymer product, and anaqueous phase. The aqueous phase is decanted and the remaining organicphase is stripped of its solvent component It is most convenient toaccomplish this strip by pumping the organic phase into boiling ornear-boiling water. As the solvent is flashed off, particles of thebrominated styrenic polymer product form in and separate from theresidual liquid phase as a precipitate, and if desired, concurrently asuitable amount of the base can be incorporated into the particulatebrominated polystyrene as it is being formed. If desired, a surfactant,such as dioctyl sulfosuccinate sodium salt, can be added to the hotwater. The amount of dioctyl sulfosuccinate, if used, can be within therange of from about 0.01 to about 0.05 wt %, based upon the total weightof water and surfactant. The precipitate can be recovered by anyliquid-solid separation technique, e.g., filtration, centrifugation,etc. The recovered precipitate is then dried.

Analytical Methods

Since brominated styrenic polymers have good, or at least satisfactory,solubility in solvents such as tetrahydrofuran (THF), the determinationof the total bromine content for the brominated styrenic polymers iseasily accomplished by using conventional X-Ray Fluorescence techniques.The sample analyzed is a dilute sample, say 0.1±0.05 g brominatedpolystyrene in 60 mL THF. The XRF spectrometer can be a Phillips PW1480Spectrometer. A standardized solution of bromobenzene in THF is used asthe calibration standard. The total bromine values described herein andreported in the Examples are all based on the XRF analytical method.

To determine the ionic bromine content of brominated styrenic polymers,the procedure used involves dissolving a sample of the polymer in asuitable organic solvent medium and titrating the solution with astandard solution of silver nitrate. In particular, a 2.0 gram sample ofthe brominated styrenic polymer weighed to the nearest 0.1 mg is placedin a 600 mL beaker, followed by 200 mL of tetrahydrofuran (THF), and astir bar. The solids are stirred until completely dissolved. To thissolution is added 50 mL of toluene, and the mixture is stirred.Immediately prior to conducting the titration, 50 mL of acetone, then 50mL of isopropyl alcohol, and then 10 mL of glacial acetic acid are addedto the sample mixture. The sample is then titrated immediately withstandardized 0.01 N AgNO₃ using an automatic potentiometric titratorsuch as a Metrohm 670, 716, or 736, or equivalent. Reagent grade(A.C.S.) THF, toluene, acetone, isopropyl alcohol, and acetic acid areused in the procedure. The analysis is conducted using duplicatesamples, plus a determination on a blank sample conducted in identicalfashion except using no polymer. If both ionic bromine and ionicchlorine are present, the bromide titrates first. The distance betweenthe inflection points is the chloride titre. The average of the twosample determinations is reported. However, if duplicate samples do notagree within less than 10% of each other, an additional replicate sampleis analyzed in the same way, and the average of the three analyses isreported to three significant digits. The calculation for ionic bromineor chlorine are as follows:$\text{Ionic bromine (ppm)}\quad = \frac{{mL}\quad \text{AgNO}_{3} \times \quad \text{normality of}{AgNO}_{3} \times \quad (7.99) \times 10^{4}}{\text{sample weight in grams}}$$\text{Ionic chlorine (ppm)} = \frac{{mL}\quad \text{AgNO}_{3} \times \quad \text{normality of}{AgNO}_{3} \times \quad (3.545) \times 10^{4}}{\text{sample weight in grams}}$mL  AgNO₃ = mL  required for sample   − mL  required for blank

To determine the color attributes of the brominated polymers of thisinvention, use is again made of the ability to dissolve brominatedstyrenic polymers in easy-to-obtain solvents, such as chlorobenzene. Theanalytical method used is quite straight-forward. Weigh 5 g±0.1 g of thebrominated polystyrene into a 50 mL centrifuge tube. To the tube alsoadd 45 g ±0.1 g chlorobenzene. Close the tube and shake for 1 hour on awrist action shaker. After the 1 hour shaking period, examine thesolution for undissolved solids. If a haze is present, centrifuge thesolution for 10 minutes at 4000 rpm. If the solution is still not clear,centrifuge an additional 10 minutes. Should the solution remain hazy,then it should be discarded as being incapable of accurate measurement.If, however, and this is the case most of the time, a clear solution isobtained, it is submitted for testing in a HunterLab ColorQuest SphereSpectrocolorimeter. A transmission cell having a 20 mm transmissionlength is used. The colorimeter is set to “Delta E-lab” to report coloras ΔE and to give color values for “L,” “a” and “b”.

DSC values were obtained with a TA Instruments DSC Model 2920. Sampleswere heated from 25° C. to 400° C. at 10° C./min under nitrogen.

Thermogravimetric analysis (TGA) is used to test the thermal behavior ofthe brominated styrenic polymers of this invention. The TGA values areobtained by use of a TA Instruments Thermogravimetric Analyzer. Eachsample is heated on a Pt pan from 25° C. to about 600° C. at 10° C./minwith a nitrogen flow of 50-60 mL/min.

To determine thermal stability and estimate the corrosive potential of asample, the following test procedure as described in U.S. Pat. No.5,637,650 is used. Each sample is run in duplicate. A 2.00±0.01 g sampleis placed into a new clean 20×150 mm test tube. With a neoprene stopperand Viton® fluoroelastomer tubing, the test tube is connected to anitrogen purge line with exit gas from the test tube being passedsuccessively through subsurface gas dispersion frits in three 250 mLsidearm filter flasks each containing 200 mL of 0.1 N NaOH and 5 dropsof phenolphthalein. With a constant nitrogen purge at 0.5 SCFH, the testtube is heated at 300° C. in a molten salt bath (51.3% KNO₃/48.7% NaNO₃)for 15 minutes followed by 5 minutes at ambient temperature. The testtube containing the sample is then replaced with a clean dry test tube,and the apparatus is purged with nitrogen for an additional 10 minuteswith the empty test tube in the 300° C. salt bath. The test tube, tubingand gas dispersion tubes are all rinsed with deionized water, and therinse is combined quantitatively with the solutions in the threecollection flasks. The combined solution is acidified with 1:1 HNO₃ andtitrated with 0.01 N AgNO₃ using an automatic potentiometric titrator(Metrohm 670, 716, 736, or equivalent). Results are calculated as ppmHBr, ppm HCl, and ppm HBr equivalents as follows:

ppm HBr=(EP 1)(N)(80912)/(sample wt.)

ppm HCl=(EP 2−EP 1)(N)(36461)/(sample wt.)

ppm HBr equivalents=(EP 2)(N)(80912)/(sample wt.)

where EP(x)=mL of AgNO₃ used to reach end point x; and N=normality ofAgNO₃. The tubing is thoroughly dried with nitrogen before the nextanalysis. Each day before the first sample, three empty clean test tubesare run as blanks to assure there is no residual hydrogen halide in thesystem.

The M_(w) values were obtained by GPC using a Waters model 510 HPLC pumpand, as detectors, a Waters Refractive Index Detector, Model 410 and aPrecision Detector Light Scattering Detector, Model PD2000. The columnswere Waters, μStyragel, 500 Å, 10,000 Å and 100,000 Å. The autosamplerwas a Shimadzu, Model Sil 9A. A polystyrene standard (M_(w)=185,000) wasroutinely used to verify the accuracy of the light scattering data. Thesolvent used was tetrahydrofuran, HPLC grade. The test procedure usedentailed dissolving 0.015-0.020 g of sample in 10 mL of THF. An aliquotof this solution is filtered and 50,μL is injected on the columns. Theseparation was analyzed using software provided by Precision Detectorsfor the PD 2000 Light Scattering Detector.

The calculated theoretical M_(w) values were obtained in accordance withthe equation:${\text{Theoretical}\quad M_{w}{BrPS}} = {{M_{w}{PS}} + \frac{\left( {M_{w}{PS}} \right)\left( {{{Atom}.\quad {wt}.\quad {Br}} - {{Atom}.\quad {wt}.\quad H}} \right)\left( {{Mol}.\quad {wt}.\quad {Sty}.} \right)\quad (0.01)\left( {{wt}\quad \% \quad {Br}} \right)}{{\left( {{Atom}.\quad {wt}.\quad {Br}} \right)\left( {{{Mol}.\quad {wt}}{\quad \quad}{{Sty}.}} \right)} - {\left( {{{Atom}.\quad {wt}.\quad {Br}} - {{Atom}.\quad {wt}.\quad H}} \right)\left( {{Mol}.{\quad \quad}{wt}.\quad {Sty}.} \right)(0.01)\left( {{wt}\quad \% \quad {Br}} \right)}}}$

As used throughout this application, “PS” is used interchangeably withand meant to designate polystyrene, while “Sty” means styrene. The term“M_(w)” means weight average molecular weight as determined by GPC(light scattering detector) described infra.

Substrate Polymer, Other Components, Proportions

Particular thermoplastics with which the foregoing brominated styrenicpolymers can be blended pursuant to further embodiments of thisinvention include polyethylene terephthalate, polybutyleneterephthalate, polycyclohexylene dimethylene terephthalate,polytrimethylene terephthalate, blends or mixtures of two or more ofthese, and analogous copolymeric thermoplastic polyesters, especiallywhen filled or reinforced with a reinforcing filler such as glass fiber.Preferred thermoplastic polyesters are polyethylene terephthalate andpolybutylene terephthalate. Polyamide thermoplastics, such as polyamide6, polyamide 6,6, polyamide 12, etc., again preferably when glassfilled, can also be effectively flame retarded in like manner.Conventional additives, such as flame retardant synergists,antioxidants, UV stabilizers, pigments, impact modifiers, fillers, acidscavengers, blowing agents, and the like, can be included with theformulations as is appropriate. Preferred polymer blends of thisinvention do contain a flame retardant synergist or glass fiber filleror reinforcement, and most preferably both a synergist, and areinforcing fiber and/or filler.

The brominated styrenic polymer flame retardants of this invention areused in flame retardant amounts, which typically are within the range offrom about 5 to about 20 wt %, the wt % being based on the total weightof the thermoplastic polymer formulation or blend. When used, the amountof reinforcing fillers such as glass fiber will typically be in therange of up to about 50 wt % based on the total weight of the finishedcomposition. The amount of flame retardant synergist, when used, such asantimony trioxide, antimony pentoxide, sodium antimonate, potassiumantimonate, iron oxide, zinc borate, or analogous synergist generallywill be in the range of up to about 12 wt % based on the total weight ofthe finished composition.

Masterbatch compositions wherein the components except for the substratethermoplastic polymer are in suitable relative proportions but areblended in a smaller amount of the substrate polymer, are also withinthe scope of this invention. Thus, this invention includes compositionswhich comprise at least one thermoplastic polymer such as a polyalkyleneterephthalate or a nylon polymer with which has been blended abrominated styrenic polymer (preferably a brominated polystyrene) ofthis invention in a weight ratio (substrate polymer:brominatedpolystyrene) in the range of, say, 1:99 to 70:30. Such masterbatchblends need not, but may also contain filler or reinforcing fiber and/orat least one flame retardant synergist such as iron oxide, zinc borate,or preferably an antimony oxide synergist such as antimony trioxide,antimony pentoxide, sodium antimonate, or potassium antimonate. Typicalexamples of reinforcing agents or fillers that can be used includelow-alkali E-glass, carbon fibers, potassium titanate fibers, glassspheres or microballoons, whiskers, talc, wollastonite, kaolin, chalk,calcined kaolin, and similar substances. Sizing agents can be used withsuch reinforcing agents or fillers, if desired. A number of suitableglass-filled polyalkylene terephthalates or nylon molding compositionsare available on the open market, and these can be used in preparing thecompositions of this invention.

Also provided by this invention are additive blends composed of abrominated styrenic polymer of this invention and a synergist such as,for example, a blend of 75 parts by weight of a brominated polystyreneand 25 parts by weight of a synergist such as antimony trioxide,antimony pentoxide, sodium antimonate, potassium antimonate, iron oxide,zinc borate, or analogous synergist. Typically, such blends will containin the range of about 70 to about 98 parts by weight of the brominatedpolystyrene and about 30 to about 2 parts by weight of the synergist,with the total of the two components being 100 parts by weight. Suitableamounts of other suitable additive components can also be included insuch additive blends.

Various known procedures can be used to prepare the blends orformulations constituting such additional compositions of thisinvention. For example, the polyalkylene terephthalate polymer or anylon polymer and the brominated styrenic polymer such as brominatedpolystyrene and any other components or ingredients to be incorporatedinto the finished blend can be blended together in powder form andthereafter molded by extrusion, compression, or injection molding.Likewise, the components can be mixed together in a Banbury mixer, aBrabender mixer, a roll mill, a kneader, or other similar mixing device,and then formed into the desired form or configuration such as byextrusion followed by comminution into granules or pellets, or by otherknown methods.

The following Examples are presented for purposes of illustration andare not to be construed as imposing limitations on the scope of theinvention.

Examples 1-3 give preferred general procedures for producing brominatedpolystyrene of this invention.

EXAMPLE 1

A mixture of 770.0 g bromochloromethane (BCM, 9 ppm water) and 2.775 gpowdered AlCl₃ was prepared in a 5-L jacketed glass reactor equippedwith a mechanical paddle stirrer, condenser, and thermowell. A jacketedglass mixing tee was mounted on an inlet port on the reactor to whichbromine (533.35 g, 3.337 mole) and a solution of 134.00 g (1.287/n mole)polystyrene (Mitsubishi Kasei Polytex, M_(w)=270,000) in 1204 g BCM werepumped at average rates of 8.74 g/min and 20.27 g/min, respectively. Thereactor and mixing tee were cooled with a circulating glycol bath tomaintain a temperature of 0° C. to 2° C. throughout the 1 hour feed timeand subsequent 1 hour cook. The reaction mixture was then washed withwater and neutralized with a mixture of aqueous sodium gluconate, sodiumsulfite, and sodium hydroxide. After diluting the organic phase withadditional BCM (1450 g), the solution was added dropwise to 1.8 L hot(90° C.-94° C.) water containing 0.25 g dioctyl sulfosuccinate sodiumsalt (surfactant) to precipitate the product and distill the solvent.The slurry was filtered and the off-white solid was washed with water.Drying to constant weight at 150° C. gave 389.8 g.

EXAMPLE 2

A 7.209 g (54.1 mmol) portion of powdered aluminum chloride wassuspended (stirred at 250 rpm) in 1549.83 g of dry (10 ppm water)bromochloromethane (BCM) in a 5-L jacketed reaction flask cooled to 0°C. by a circulating glycol bath. A 10.00 wt % solution of PS (360.96 g,3.4657/n mol) in dry BCM (3250.44 g) was prepared in a second 5-L flask.The PS used was Dow Styron® 612 which had a M_(w) of 190,000. The PSsolution was pumped from the bottom valve of this feed reservoir to ajacketed, glycol-cooled mixing tee mounted on the reaction flask. At thesame time, bromine was pumped from a tared feed reservoir to the samemixing tee where it combined with the polystyrene solution beforedropping into the stirred catalyst suspension in the reaction flask. TwoMasterflex® 7550-90 pumps were used. The PS feed system used anall-Teflon feed line with pump head 77390 operating at a constant speedof 60 rpm. This provided a constant feed rate of 21.02/n mmol PS/min(21.89 g/min). The bromine feed system used a combination of Teflon andViton tubing with pump head 7518-10 operating at a rate of 70.05mmol/min for the first 18 min, 38.80 mmol/min for 18-23 min, and 56.75mmol/min for 23-165 min. Both feeds ended at 165 min. The overall moleratio of Br₂/PS was 2.70. A rinse of 260.95 g of dry BCM was used forthe PS solution feed system to assure complete transfer of the polymerto the reaction flask. The reaction temperature was maintained at 0° C.to 4° C. throughout the addition and subsequent 2.3 hour cook period(with nitrogen purge of the reactor overhead). The weight increase forthe caustic exit gas scrubber was 665.4 g (87.8% of theory for HBr). Thecatalyst was deactivated by addition of 125.0 g of a 10 wt % aqueoussolution of sodium gluconate. A 63.41 g portion of 10 wt % aqueoussodium sulfite was added, and the pH was adjusted to 14 by addition of423.0 g of 10 wt % aqueous NaOH. After dilution with BCM (1334.6 g), theorganic phase was separated and then washed with water (1011.8 g). Theproduct was recovered from the organic phase by addition to vigorouslystirred hot (90° C.-94° C.) water to which was added 1.23 g of thesodium salt of dioctyl sulfosuccinate. The solvent distilled from thehot water leaving a slurry of brominated polystyrene product in water.After suction filtering, the off-white solid was rinsed with water anddried to a constant weight of 1085.98 g (97.9% yield) in a vacuum oven(150° C./2 torr/5 hr). The ionic bromine content of the brominatedpolystyrene so produced was only 88 ppm by weight.

EXAMPLE 3

The procedure of Example 2 was followed except that: a 2 L flask and 40g of polystyrene were used; the AlCl₃ wt % (based on polystyrene) was2.0 wt %; the feed mole ratio of bromine to polystyrene was 3.33; thetotal equivalents of bromine was 2.78; the temperature range was 0° C.to 5° C.; the feed times for the bromine/polystyrene was 32 min/38 min;and the cook time was 150 minutes.

Example 4, wherein all parts are by volume unless otherwise specified,illustrates a preferred purification process for removing ionic brominefrom brominated polystyrene during the course of preparing the polymer.

EXAMPLE 4

A brominated polystyrene reaction mass (1500 parts), formed by reactingbromine with a 10 wt % solution of polystyrene in bromochloromethane(BCM) using aluminum chloride as catalyst, was quenched in 450 parts ofwater, and thoroughly mixed for 15 minutes. A sample of the quenchedreaction mass (Sample A) was taken for use in the purification processdescribed below. The aqueous and organic phases were allowed to settleand the aqueous phase was removed by decantation. The organic phase wasthen brought to pH 12 by the addition of 50 parts of fresh water and 25parts of 25 wt % sodium hydroxide solution. This mixture was thoroughlymixed. Any residual bromine was scavenged by addition to the mixture of1.7 parts of 6.9 wt % sodium borohydride in 23 wt % aqueous sodiumhydroxide solution, followed by thorough mixing. A sample of theresultant organic phase (Sample B) was taken for recovery of thebrominated polystyrene without use of the following purificationprocess.

Application of the purification process to Sample A was performed asfollows: Sample A was poured into a 1000 mL glass separatory funnel. Theaqueous and organic phases were allowed to separate for 5 minutes. Theorganic phase was removed from the bottom of the funnel (325.2 grams).The aqueous layer was recovered (71.0 grams). The organic phase wasseparated into two equal halves and placed into two 8 ounce jars. Freshwater was placed into each jar for a second water wash (46.1 grams).This water level is equivalent to a ratio of 850 parts of water to 1500parts of reaction mass. Both jars were shaken for 30 minutes on aBurrell Wrist Action Shaker. The contents of both jars were poured intoand combined in a 1000 mL separatory funnel and allowed to separate for5 minutes. The organic phase was recovered from the bottom (319.5grams), and 95.3 grams of aqueous phase remained in the funnel. Freshwater (12.8 grams) was added to the organic phase to assist in pHreading using strips of pH indicator paper. The pH of the organic phasewas 5. The pH was raised to 14 by the addition of 25% by weight aqueoussodium hydroxide solution (2.4 grams). Excess bromine was scavenged bythe addition of 6.9 wt % sodium borohydride in 23 wt % aqueous sodiumhydroxide solution (0.5 gram). The brominated styrene product fromSample A was recovered by precipitation into a mixture formed from 1500grams of water and 12.6 grams of 25% by weight aqueous sodium hydroxidesolution. In conducting this precipitation operation, the water-sodiumhydroxide mixture was in a 3000 mL glass reactor, with baffles, and washeated to 100° C. The vessel was stirred by an agitator set on 500 rpm.The organic phase was fed into this reactor by a peristaltic pump, seton 42 rpm through ⅛″ polypropylene tubing into the water. The feed pointwas approximately ½″ underneath the water surface. The BCM was condensedand removed overhead. After the organic phase was fed, the watertemperature was allowed to return to 100° C. to remove any residual BCMand then cool. The brominated polystyrene product was vacuum filtered ina 2000 mL fritted glass filter. It was washed three times withapproximately 1000 mL of warm water. The solids were dried in a vacuumoven at 140° C. overnight. The ionic bromine level detected in the finalbrominated polystyrene product from Sample A was 222 ppm.

The brominated polystyrene product from Sample B, without use of theabove purification process, was recovered by use of the foregoingprecipitation procedure. The precipitation used 1500 grams of water and13.0 grams of 25% by weight sodium hydroxide aqueous solution followedby three washings with warm water. The ionic bromine level detected inthe final brominated polystyrene product recovered from Sample B was1810 ppm.

In carrying out the purification process illustrated in Example 4,effective use can be made of coalescing filters and/or a liquid-liquidextraction column. The principles involved in the design and operationof such equipment is known and reported in the literature. Anyoneinterested in pursuing such information can refer, for example, to I.Bartik, Liquid/Liquid Separation Through The Use of Coalescence, a paperpresented on Feb. 8, 1977 at The Filtration Society, New EnglandChapter, Sturbridge, Mass. 01566; and McCabe and Smith, Unit Operationsof Chemical Engineering, Third Edition, McGraw-Hill Book Company, pages619-627; or other similar sources. In using a liquid-liquid extractiontower the water should be introduced into the column below the incomingcountercurrent flow of the crude organic phase to the tower, so that thewater extract is taken from the upper portion of the tower and theextracted organic phase is removed from the lower portion of the tower.

Comparative Examples CE-1 and CE-2 describe the preparation ofbrominated polystyrene in accordance with the teachings of U.S. Pat. No.5,532,322, which issued in 1996.

COMPARATIVE EXAMPLE CE-1

A solution of 75.10 g (0.721/n mole) of polystyrene (Mitsubishi KaseiPolytex, M_(w)=270,000) in 750 g of 1,2-dichloroethane (EDC, containing12 ppm water) was prepared in a 5 L jacketed glass reactor equipped witha mechanical paddle stirrer, condenser, and thermowell. The temperatureof the reaction was controlled with an ethylene glycol circulating bathon the reactor jacket. After cooling to 15° C., 11.03 g of antimony(III) oxide was added to the polystyrene solution. A previously preparedsolution of 149.7 g (0.937 mole) bromine and 66.3 g (0.935 mole)chlorine in 505 g cold (−5° C.) EDC was added to the reactor under theliquid surface through a diptube attached to the cooled bromine chloridefeed reservoir. The reaction temperature was slowly increased from 10°C. to 25° C. during the 2 hour addition. The mixture was then held at30° C. until hydrogen halide evolution was complete (1.5 hr) asindicated by an end of the weight gain of the caustic scrubber on theexit gas line from the reactor. The reaction mixture was washed withwater and neutralized with aqueous sodium sulfite and caustic. Theorganic phase was then added dropwise to 3.5 L methanol to precipitatethe product. The slurry was filtered and the solid was washed withmethanol. After vacuum drying at 150° C., the light yellow solid(product 1) weighed 203.7 g.

COMPARATIVE EXAMPLE CE-2

Comparative Example CE-1 was repeated using 230.8 g (2.00 mole)commercial bromine chloride with 80.20 g (0.770/n mole) polystyrene and11.77 g Sb₂O₃. The water washed and neutralized organic phase wasdivided into two equal portions. One portion was added to 1.5 L ofmethanol as in Example CE-1 to obtain 101.6 g of light yellow solid(product A) after drying to constant weight at 150° C. The other portionwas added dropwise to 1.9 L of hot (89° C.-94° C.) water to precipitatethe product and distill the solvent. The dry light yellow solid (productB) weighed 100.3 g.

In Table 1 a compilation of the properties of the brominated polystyreneproducts produced in Examples 1-3 and Comparative Examples CE-1 and CE-2is given. In addition, the properties of Pyro-Chek 68PB flame retardantof Ferro Corporation are given. Pyro-Chek 68PB flame retardant isbelieved to be produced in accordance with the teachings of U.S. Pat.No. 4,352,909.

TABLE 1 ANALYTICAL RESULTS Example 1 2 3 CE-1 CE-2 A CE-2 B Pyro-Chek68PB Total Br (wt %) 69.5 68.9 69.8 63.48 63.10 63.00 67.2 ThermalStability¹ (ppm HBr) 380 104 85 3250 2560 3770 1960 Total Cl (wt %)<0.01 — <0.01 1.00 0.68 0.83 0.71 GPC M_(w) (light scat.) 920,000 —620,000 560,000 580,000 580,000 620,000 Calc'd. Theo. M_(w) 860,000590,000 610,000 720,000 715,000 715,000 n/d² GPC (light scat.) DSC Tg³(°C.) 190 — — 170 164 162 185 TGA 1% wt loss @ (° C.) 349 357 375 312311 293 300 Solution Color L 96.32 96.47 96.86 96.21 94.99 94.62 92.03 a−2.09 −2.45 −2.300 −2.36 −2.32 −2.33 −0.17 b 11.99 14.30 11.16 15.0716.96 17.06 23.38 ΔE 12.72 14.90 11.84 15.71 17.83 18.03 24.70¹Determined by use of the method of U.S. Pat. No. 5,637,650 describedabove. ²Calculated Theoretical M_(w) for Pyro-Chek 68PB could not bedetermined since the M_(w) of the polystyrene reactant used in 68PB itnot known. ³Tg = glass transition temperature.

Examples 5, 6, and 7 illustrate additional procedures by whichbrominated polystyrenes of this invention can be prepared.

EXAMPLE 5

A 0.910 g (6.82 mmol) portion of powdered aluminum chloride wassuspended (stirred at 250 rpm) in 190 g of dry (13 ppm water)bromochloromethane (BCM) in 1 L jacketed flask cooled to 0° C. bycirculating glycol bath. A 419.86 g portion of a 10.00 wt % solution ofpolystyrene (403.1/n mmol) in dry BCM was pumped at a constant rate of8.46 g/min (8.13 mmol/min) to a jacketed, glycol-cooled mixing teemounted on the reaction flask. At the same time, bromine was pumped at aconstant rate of 6.09 g/min (38.1 mmol/min) to the same mixing tee whereit combined with the polystyrene solution (feed mole ratio of Br₂/PS is4.69) before dropping into the stirred catalyst suspension in thereaction flask. The bromine feed was stopped after 30.0 min (1143.5mmol) and the polystyrene solution feed was stopped after 49.6 minutes(overall mole ratio of Br₂/PS is 2.84). A rinse of 160 g of dry BCM wasused for the polystyrene solution feed system to assure completetransfer of the polymer to the reaction flask. The reaction temperaturewas maintained at 0° C.-5° C. throughout the addition and subsequent 2hr cook period. The catalyst was deactivated by addition of 16.4 g of 10wt % aqueous solution of sodium gluconate, and pH was adjusted to 14 byaddition of 60.7 g of 10 wt % aqueous NaOH. The reaction mixture waswashed with 10 wt % aqueous sodium sulfite followed by a water wash. Theproduct was recovered from the organic phase by addition to vigorouslystirred hot (90° C.) water containing 0.02 wt % dioctyl sulfosuccinatesodium salt surfactant. The solvent is distilled from the hot waterleaving a slurry of the brominated polystyrene product in water. Afterfiltering, the powdery solid was rinsed with water and dried to constantweight in a vacuum oven (150° C./2 torr/5 hr). The dry solid weighed127.08 g (95% yield). The product contained 69.6 wt % total Br. In thethermal stability test referred to above, the product evolved 174 ppm ofHBr in 15 minutes at 300° C. The HunterLab solution color (10 wt % inchlorobenzene) values were L=94.58, a=−2.79, b=17.29, Delta E=18.34.

EXAMPLE 6

A Y-shaped mixing apparatus having a cooling jacket was equipped with 2feed lines, each connected to a pump. One of the feed lines was fordelivering bromine and the other was for delivering a PS and BCMsolution. Bromine (93.3 g, 31.3 mL or 0.583 mole), delivered at a rateof 1 mL/min (19.4 mmol/min), and a PS/BCM solution (22.4 g PS, 0.215 moland 97 mL or 194 g of anhydrous BCM), delivered at 4 mL/min (7.17mmol/min), were fed simultaneously from their respective feed lines intothe cooled (5° C.) Y-mixing apparatus. The resultant intimate mixturefrom the mixing apparatus was then fed into a cooled (5° C.) suspensionof 0.45 g (2 wt % based on PS) of powdered aluminum chloride in 49 mL(98 g) of anhydrous BCM. Evolved HBr was scrubbed by a caustic solutionduring the reaction. The feeds were complete in 35 minutes and themixture was cooked for 2 hours at 5° C. After water and sodium sulfitewashes, solid BrPS was isolated by precipitating from 500 mL of hot (90°C.) water as described above. A total of 66 g of BrPS (97% yield) wasobtained. The product contained 68.4 wt % total Br. In the thermalstability test referred to above, the product evolved 71 ppm of HBr in15 minutes at 300° C. The HunterLab solution color (10 wt % inchlorobenzene) values were L=96.74, a=−1.90, b=15.99, Delta E=16.44.

EXAMPLE 7

A 0.910 g (6.82 mmol) portion of powdered aluminum chloride is suspended(stirred at 250 rpm) in 190 g of dry (13 ppm water) bromochloromethane(BCM) in 1 L jacketed flask cooled to 0° C. by circulating glycol bath.A 419.86 g portion of a 10.00 wt % solution of polystyrene (403.1/nmmol) in dry BCM is pumped at a constant rate of 8.46 g/min (8.13mmol/min) to a jacketed, glycol-cooled mixing tee mounted on thereaction flask. At the same time, bromine is pumped at a constant rateof 6.09 g/min (38.1 mmol/min) to the same mixing tee where it iscombined with the polystyrene solution (feed mole ratio of Br₂/PS is4.69) before dropping into the stirred catalyst suspension in thereaction flask. The bromine feed is stopped after 30.0 min (1143.5 mmol)and the polystyrene solution feed is stopped after 30 minutes (overallmole ratio of Br₂/PS is 2.84). A rinse of 160 g of dry BCM is used forthe polystyrene solution feed system to assure complete transfer of thepolymer to the reaction flask. The reaction temperature is maintained at0° C.-5° C. throughout the addition and subsequent 45 minute cookperiod. The catalyst is deactivated by addition of 16.4 g of water. Thecrude organic and aqueous phases are allowed to settle, and the aqueousacidic phase is removed. Then the pH is adjusted to 14 by the additionof 10 wt % aqueous NaOH, and sodium borohydride is added to scavenge anyexcess bromine. The product is then recovered from the organic phase byaddition to vigorously stirred hot (90° C.) water. The solvent isdistilled from the hot water leaving a slurry of the brominatedpolystyrene product in water. After filtering, the powdery solid isrinsed with water and dried to constant weight in a vacuum oven (150°C./2 torr/5 hr).

Examples 8-21 illustrate additional preferred procedures for producingbrominated polystyrenes of this invention.

EXAMPLES 8-21

The following procedure was used in these Examples: A mixture of 1.44 g(10.8 mmol) of aluminum chloride (Aldrich, anhydrous) and 310 g of dry(10-60 ppm water after drying over molecular sieves) bromochloromethane(BCM) was stirred at 350 rpm with a paddle of Teflon® polymer in a 1 Lthree-necked jacketed round bottom flask. The flask contents were cooledto the desired temperature by circulating chilled ethylene glycolthrough the jacket. A 10 wt % solution of Dow Styron 612 polystyrene(72.2 g; 0.69 equivalents) in dry BCM (650 g) was charged to a separatevessel (500 mL graduated addition funnel). The polystyrene solution waspumped from the bottom of this feed reservoir to a vacuum jacketedmixing tee mounted on the reaction flask. The tee was maintained at thesame temperature as the reaction mixture by circulating the ethyleneglycol exiting from the flask to the tee. As the polystyrene solutionwas pumped from the reservoir, bromine (295.5 g; 1.85 mol) wassimultaneously pumped from a 125 mL graduated addition funnel to thesame mixing tee where it combined with the polystyrene solution. Theresulting red solution flowed through the jacketed, spiral column(approximately 12″ in length) and exited above the surface of thestirred catalyst suspension. Two Masterflex pumps were used for the feedto the mixing tee. The polystyrene system used an all Teflon line with aCole-Palmer 77390 pump head. The bromine feed system used a combinationof Teflon and Viton tubing with the latter being used with a Masterflex7518-10 pump head. Both feeds ended in approximately 32-35 minutes.Constant attention to feed rates was necessary in order to achievecomplete addition simultaneously. The overall mole ratio of Br₂/PS was2.7. A rinse of 57 g of dry BCM was used for the polystyrene solutionfeed system to assure complete transfer of the polymer to the reactionflask. After the addition was complete, the reaction was stirred attemperature for 45 minutes while being swept with nitrogen and was thenquenched by the addition of 13 g of a 10 wt % solution of sodiumsulfite. During the quench the material was stirred at 450 rpm and wasstirred at this rate for 5 minutes. The reaction color changed fromred/brown to a cream (light tan) during the sulfite addition. Thereaction was allowed to stand for 5 minutes and the phases wereseparated using a bottom valve on the reaction flask. After removing theaqueous phase from the reactor, the organic layer was returned to thereactor and the pH was adjusted to 14 with the use of 10 wt % aqueousNaOH (100-200 g). Additional BCM (267 g) was added, the mixture wastransferred to a separatory funnel, and the phases were allowed toseparate. Product was recovered from the organic phase by addition tohot water as follows. A 2 L three-necked creased flask equipped with amechanical stirrer, 125 mL addition funnel, thermometer, and Dean-Starktrap with a condenser was charged with 700 mL of water and heated to92-94° C. with a heating mantle. The addition funnel was filled with thecontents from the bottom phase of the separatory funnel. The feed ratefrom the addition funnel was controlled so that the condenser on theDean-Stark trap was not overloaded and so that the water temperature didnot fall below 91 ° C. BCM and some water were removed overhead whilethe product precipitated in the water as white to yellowish-whitesolids. The addition funnel was refilled as necessary to have acontinuous flow of material to the flask. After the addition wascomplete, the slurry was stirred at temperature for about 10 minutes toensure complete removal of BCM. The slurry was allowed to cool to about65° C. and collected on a Buchner funnel using suction filtrationthrough #2 filter paper. About 300 mL of hot water was used to rinse theflask and the filter cake. The solids were transferred to a 2 L beaker,thoroughly mixed with 400 mL of water and reisolated by suctionfiltration. The solids were air dried overnight and then dried at 150°C. in a vacuum oven (1-5mm Hg) until a constant weight (180-200 g) wasachieved. The product was powdered with a mortar and pestle prior toanalysis (see Table 2).

TABLE 2 ANALYTICAL RESULTS Example 8 9 10 11 12 13 14 Reaction Temp. (°C.) −10 −10 −10 −10 0.00 0.00 0.00 Total Br (wt %) 68.7 68.8 69.2 68.369.3 70.1 68.5 Thermal Stability (ppm HBr) 312 267 289 328 330 196 115Hunter Lab Soln. Color (10% PhCl) L 98.09 97.64 97.74 97.75 97.14 97.5196.79 a −1.70 −1.83 −1.51 −1.54 −2.12 −1.59 −2.33 b 7.98 8.56 7.55 8.109.78 7.90 11.08 ΔE 8.38 9.07 8.02 8.55 10.40 8.43 11.77 TGA 1% Wt loss351 353 358 353 355 356 347 Temp/N₂(° C.) (GPC mol. Wt. (light scat.detect.) M_(w) (× 10³) 595 601 580 631 634 572 645 Calc'd M_(w) (× 10³)591 592 600 584 602 617 587 M_(w)/M_(w) (Calc'd) 1.01 1.02 0.97 1.081.05 0.93 1.10 ANALYTICAL RESULTS Example 15 16 17 18 19 20 21 ReactionTemp. (° C.) 0.00 10 10 10 20 20 20 Total Br (wt %) 68.6 69.0 69.1 68.969.2 68.7 68.7 Thermal Stability (ppm 74 222 203 194 349 313 249 HBr)Hunter Lab Soln. Color (10% PhCl) L a 97.31 96.47 96.88 96.56 94.4094.70 94.43 b −2.32 −3.12 −2.83 −2.57 −3.18 −3.40 −3.23 ΔE 10.10 14.6312.98 13.09 22.79 22.17 23.92 TGA 1% Wt loss 10.71 15.38 13.65 13.7723.68 23.05 24.78 Temp/N₂ (° C.) 351 352 347 349 342 347 344 (GPC mol.Wt. (light scat. detect.) M_(w) (× 10³) 583 673 694 819 886 863 831Calc'd M_(w) (× 10³) 589 596 598 594 600 591 591 M_(w)/M_(w) (Calc'd)0.99 1.13 1.16 1.38 1.48 1.46 1.41

The ionic bromine content of the brominated polystyrene formed inExample 14 was measured and found to be only 320 ppm by weight.

Commonly-owned application Ser. No. 09/066,172, filed Apr. 24, 1998,describes processes in which a suitable amount of aqueous base isemployed to improve the thermal stability of the resultant brominatedpolystyrene. It is to be noted that the use of such processes, whiledesirable, is not required pursuant to this invention, as the excellentresults referred to hereinabove were achieved without using brominatedpolystyrene formed in this way. Thus, the process procedures which arefully described in this commonly-owned copending application, constituteoptional, but entirely suitable procedures for producing brominatedpolystyrenes of the present invention.

Inclusion of the suitable amount of inorganic alkali metal base such asNaOH or KOH into the brominated polystyrenes of Examples 8-21 ispreferably accomplished substantially in the manner described in Example22, infra, by utilizing a suitable excess of aqueous NaOH (or KOH) whenprecipitating the brominated polystyrene from BCM, and eithereliminating the final water wash step or substituting an aqueous NaOH(or KOH) solution as the final wash. Alternatively, and less preferably,brominated polystyrenes formed as described in Examples 8-21 infinely-divided or powder form can be powder blended with suitablequantities of powdered alkali metal base such as sodium hydroxide,sodium acetate, or potassium hydroxide.

EXAMPLE 22

The procedure of Example 1 is repeated and in the step wherein thereaction mixture is washed with water and neutralized with a mixture ofaqueous sodium gluconate, sodium sulfite, and sodium hydroxide, theamount of the aqueous sodium hydroxide is such that a dried sample ofthe brominated polystyrene composition produced in the process, whensubjected to the following pH determination procedure, gives an aqueousextract having a pH of 9.3. The procedure for determining pH of thebrominated polystyrene composition is as follows: Place in a beaker 1gram to 1.5 grams of a representative sample, weighed to the nearest 0.1gram, and dissolve same in 50 mL of BCM. Then add 50 mL of water whichhas been boiled to remove carbon dioxide and has a pH of 7. Vigorouslystir the resultant mixture with a magnetic stirrer such that the twoliquid phases are intimately mixed for 2 to 5 minutes. Then reduce thestirrer speed such that the two phases separate in the beaker, and lowerthe pH electrode in the upper layer only. Measure the pH of the upperlayer using a Hach EC-10 pH meter (or equivalent) that has beencalibrated the same day.

It is to be understood that the components referred to by chemical nameor formula anywhere in the specification or claims hereof, whetherreferred to in the singular or plural, are identified as they existprior to coming into contact with another substance referred to bychemical name or chemical type (e.g., another component, a solvent, oretc.). It matters not what preliminary chemical changes, transformationsand/or reactions, if any, take place in the resulting mixture orsolution as such changes, transformations, and/or reactions are thenatural result of bringing the specified components together under theconditions called for pursuant to this disclosure. Thus, the componentsare identified as ingredients to be brought together in connection withperforming a desired operation or in forming a desired composition. Eventhough the claims hereinafter may refer to substances, components and/oringredients in the present tense (“comprises,” “is,” etc.), thereference is to the substance, component or ingredient as it existed atthe time just before it was first contacted, blended or mixed with oneor more other substances, components and/or ingredients in accordancewith the present disclosure. The fact that a substance, component oringredient may have lost its original identity through a chemicalreaction or transformation during the course of contacting, blending ormixing operations, if conducted in accordance with this disclosure andwith the application of common sense and the ordinary skill of achemist, is, thus, wholly immaterial for an accurate understanding andappreciation of the true meaning and substance of this disclosure andthe claims thereof.

Each and every patent or publication referred to in any portion of thisspecification is incorporated in toto into this disclosure by reference,as if fully set forth herein.

This invention is susceptible to considerable variation in its practice.Therefore, the foregoing description is not intended to limit, andshould not be construed as limiting, the invention to the particularexemplifications presented hereinabove. Rather, what is intended to becovered is as set forth in the ensuing claims and the equivalentsthereof permitted as a matter of law.

That which is claimed is:
 1. A brominated styrenic polymer that has anionic bromine content of 2000 ppm or less, and at least two of thefollowing additional characteristics: a) a TGA temperature for 1% weightloss which is 340° C. or higher and a chlorine content, if any, of lessthan about 700 ppm Cl, b) an actual M_(w) which is within about 20% ofits calculated theoretical M_(w), the theoretical M_(w) being based uponthe actual bromine content of the brominated styrenic polymer and theM_(w) of the styrenic polymer reactant used to produce the brominatedstyrenic polymer, c) essentially no content of impurities selected fromthe group consisting of bromodichloroethane, dibromochloroethane,dibromodichloroethane, tribromochloroethane, and ethylene dichloride. 2.A brominated styrenic polymer of claim 1 wherein said ionic brominecontent is 1500 ppm or less.
 3. A brominated styrenic polymer of claim 1wherein said ionic bromine content is 1000 ppm or less.
 4. A brominatedstyrenic polymer of claim 1 wherein said polymer has all three of saidadditional characteristics.
 5. A brominated styrenic polymer of claim 1wherein said polymer has all three of said additional characteristics,and additionally has a thermal stability in the Thermal Stability Testof 1500 ppm HBr or less.
 6. A brominated styrenic polymer of claim 1wherein said polymer has a total bromine content of at least about 60 wt%.
 7. A brominated styrenic polymer of claim 1 wherein said polymer hasa total bromine content of at least about 67 wt %.
 8. A brominatedstyrenic polymer of claim 1 wherein said polymer has at least theadditional characteristics of a) with the proviso that the chlorinecontent, if any, is less than about 100 ppm Cl.
 9. A brominated styrenicpolymer of claim 8 wherein said ionic bromine content is 1000 ppm orless, and wherein said polymer has a thermal stability in the ThermalStability Test of 1000 ppm HBr or less.
 10. A brominated styrenicpolymer of claim 8 wherein said ionic bromine content is 500 ppm orless, and wherein said polymer has a thermal stability in the ThermalStability Test of 500 ppm HBr or less.
 11. A brominated styrenic polymerof claim 1 wherein said polymer has at least additional characteristicb).
 12. A brominated styrenic polymer of claim 11 wherein said ionicbromine content is 1000 ppm or less, and wherein said polymer has athermal stability in the Thermal Stability Test of 1000 ppm HBr or less.13. A brominated styrenic polymer of claim 11 wherein said ionic brominecontent is 500 ppm or less, and wherein said polymer has a thermalstability in the Thermal Stability Test of 500 ppm HBr or less.
 14. Abrominated styrenic polymer of claim 1 wherein said polymer has at leastadditional characteristic c).
 15. A brominated styrenic polymer of claim14 wherein said ionic bromine content is 1000 ppm or less, and whereinsaid polymer has a thermal stability in the Thermal Stability Test of1000 ppm HBr or less.
 16. A brominated styrenic polymer of claim 14wherein said ionic bromine content is 500 ppm or less, and wherein saidpolymer has a thermal stability in the Thermal Stability Test of 500 ppmHBr or less.
 17. A brominated styrenic polymer of any of claims 8-16wherein said polymer is a brominated polystyrene having a total brominecontent of at least about 67 wt %.
 18. A brominated styrenic polymer ofclaim 1 wherein said polymer has at least additional characteristics a)and b).
 19. A brominated styrenic polymer of claim 1 wherein saidpolymer has at least additional characteristics a) and c).
 20. Abrominated styrenic polymer of claim 1 wherein said polymer has at leastadditional characteristics b) and c).
 21. A brominated styrenic polymerof claim 1 wherein said polymer has at least additional characteristicc), and wherein the total chlorine content of said polymer, if any, isless than about 100 ppm Cl.
 22. A brominated styrenic polymer of any ofclaims 18-21 wherein said polymer is a brominated polystyrene having atotal bromine content of at least about 67 wt %, and wherein said ionicbromine content is 500 ppm or less.
 23. A brominated polystyrenecharacterized in that it has: A) an ionic bromine content of 1000 ppm orless; B) a TGA temperature for 1% weight loss which is 340° C. orhigher; C) a chlorine content, if any, of less than about 100 ppm Cl; D)a thermal stability in the Thermal Stability Test of 1500 ppm HBr orless; E) an actual M_(w) which is within about 20% of its calculatedtheoretical M_(w), the theoretical M_(w) being based upon the actualbromine content of the brominated styrenic polymer and the M_(w) of thestyrenic polymer reactant used to produce the brominated styrenicpolymer; and F) essentially no content of impurities selected from thegroup consisting of bromodichloroethane, dibromochloroethane,dibromodichloroethane, and tribromochloroethane.
 24. A brominatedpolystyrene of claim 23 wherein said thermal stability in the ThermalStability Test 1000 ppm HBr or less, wherein said actual M_(w) is withinabout 10% of said calculated theoretical M_(w), and wherein saidbrominated polystyrene has a total bromine content of at least about 60wt %.
 25. A brominated polystyrene of claim 24 wherein said thermalstability in the Thermal Stability Test 500 ppm HBr or less.
 26. Abrominated polystyrene of claim 25 wherein said total bromine content isat least about 67 wt %.
 27. A composition which comprises athermoplastic polymer with which has been blended a flame retardantamount of a brominated styrenic polymer of claim
 1. 28. A compositionwhich comprises a thermoplastic polymer with which has been blended aflame retardant amount of a brominated polystyrene of claim
 26. 29. Acomposition of claim 27 wherein said thermoplastic polymer is aglass-filled nylon polymer.
 30. A composition of claim 28 wherein saidthermoplastic polymer is a glass-filled nylon polymer.
 31. A molded orextruded article or shape formed from a composition of claim
 27. 32. Amolded or extruded article or shape formed from a composition of claim28.